The humidity isn't really a problem for the shoot as long as the camera is brought up to the same temperature as the humid room beforehand. If it's the same temp (or warmer) then the water vapour will not condense on/ in the camera. Putting it in a dry room/ box beforehand with a fan heater on and checking the temperature regularly should do the job.

After the shoot, the camera will be full of nice moist air which will condense if then moved to a colder room. If you immediately put the camera back into the room/ box it came from and keep it warm, that vapour will dissipate.

If you wanted to be double sure you could try wrapping the entire camera in cling film, just leaving the business ends of the LCD and lens free, before entering the humid room. Bit fiddly but it could be done.

no way, if your are working in a 100% humidity , you can wrap your camera in anything, it will not prevent vapor to go inside.
water is like sand, it goes everywhere it is not supposed to be if you just let it go.
Since it could not immediately damage your camera, there is a big chance that oxydation will show after a while (could take weeks, even tape can stay sticky for days if not rewinded).
the only solution is to use an airtight case (underwater bag would be nice).
if you do not find one, find a piece of glasse and a transparent plastic bag.
put the camera inside and glue the bag aperture on the glass with some plastic tape.
then apply the glass to the lense. you will be able to operate the cam through the thin plastic., and even to fix it on a tripod (add a piece of tape to consolidate the hole made by the screw).
the top caution would be to inflate slightly the bag with some dry air (from a dust remover spray) from time to time.

One other thing I forgot to mention... if you make your own underwater case with glass in the front, you have to make sure your lens is pressed directly against the glass, otherwise you'll see a reflection of your own lens from that piece of glass. This is harder to accomplish than you think, that's why we just bought the Ewa Marine after finding out there was a reflection in every shot of our homemade case.

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